1. Field of the Invention
The present invention relates to a method of and an apparatus for winding a magnetic tape onto a tape reel which prevents the magnetic tape from being partially irregularly wound and, as a result, forming lateral protrusions in a magnetic tape roll.
2. Description of Related Art
It has been conventional to use magnetic tape cartridges of a helical scan type which are advantageous to the realization of mass storage digital data backup devices for personal computers, workstations and host computers. Single reel magnetic tape cartridges which have a single tape reel contained for rotation in a cartridge case have been known as one of such the magnetic tape cartridges. When loading a magnetic recording equipment with such a single reel magnetic tape cartridge, the magnetic recording equipment draws a magnetic tape out of the single reel magnetic tape cartridge by pulling a leader block at an leading end of the magnetic tape by a tape drive mechanism in order to record information on or to read information from the magnetic tape, and rewinding the magnetic tape onto a tape reel in the magnetic tape cartridge after recording or reading of the information.
Reference is now made to FIGS. 4, 5 and 6A-6C for the purpose of providing a brief background that will enhance an understanding of the present invention. Generally speaking and, as shown in FIG. 4, a single reel magnetic tape cartridge (which is hereinafter refereed to as a magnetic tape cartridge) 100 comprises a plastic cartridge case 10 and a plastic tape reel 40 installed for rotation in the cartridge case 10. The cartridge case 10 is made up of two mating case shell halves, namely a top case shell half 20 and a bottom case shell half 30 coupled together with setscrews. The tape reel 40 is made up of upper and lower flanges 41 and 42. The lower flange 42 comprises a hollow reel hub 421 in the shape of cylindrical core around which a magnetic tape 9 is wound and a flange section 422 which are made as an integral piece. The flange section 422 has a center opening 42B having an inner diameter smaller than a bore diameter of the hollow reel hub 421. The upper flange 41 is fixedly connected to the reel hub 421 by ultrasonic welding. The tape reel 40 is provided with a brake button 52 installed within the hollow reel hub 421 and a reel plate 53 secured to the lower flange section 422. The brake button 52 has a peripheral gear 52A operative as braking means engageable with an internal gear 42A formed at the bottom of the hollow reel hub 421. The magnetic tape cartridge 100 is provided with a coil spring 51 for forcing the brake button 52 into the hollow reel hub 421 until the peripheral gear 52A engages with the internal gear 42A of the hollow reel hub 421 so as thereby to prevent the tape reel 40 from rotating while the magnetic tape cartridge 100 is not in-use. The reel plate 53, which is made of a magnetizable metal, is magnetically attracted by a rotary drive shaft of an external memory device (not shown) when the magnetic tape cartridge 100 is set in the external memory device. The center opening 42B of the flange section 422 permits a brake releasing spindle of a read-write head (not shown) of the external memory device to come into the hollow reel hub 421 and pushes the brake button 52 against the coil spring 51 upward as seen in FIG. 4 so as thereby to disengage the peripheral gear 52A of the brake button 52 from the internal gear 42A of the hollow reel hub 421. In this manner, whenever the magnetic tape cartridge 100 is set in the external memory device, the tape reel 40 is permitted to rotate. The cartridge case 10 has a tape egress/ingress opening 11 located at one corner thereof which permits tape movement into and out of the cartridge interior. A leader block or pin 80 attached to a leading end of the magnetic tape 9 is releasably held in the tape egress/ingress opening 11. This leader block 80 is engaged and pulled out of the tape egress/ingress opening 11 by a drag pin 90 provided on the tape drive unit of the magnetic recording equipment when magnetic tape cartridge 100 is set in the external memory device. The drag pin 90 guides the magnetic tape 9 to a take-up reel (not shown) of the external memory device through the read-write head.
Referring to FIG. 5 showing a magnetic recording equipment 1 for use with in which the magnetic tape cartridge 100 shown in FIG. 4, the magnetic recording equipment 1 comprises a cartridge loading section 2 in which the magnetic tape cartridge 100 is set, a tape winding section 3 in which a take-up reel 6 is installed and a read-write head 7 and is provided with a number of guide rollers 8 for defining a tape path along which a magnetic tape 9 unwound from the in the magnetic tape cartridge 100 is guided to the take-up reel 6. When the magnetic tape cartridge 100 is set in the magnetic recording equipment 1, a tape drive unit (not shown) is activated to bring the drag pin 90 (see FIG. 4) into engagement with the leader block 80 and then pull the drag pin 90 out of the cartridge case 10, and further leads the leader block 80 to the tale-up spool 6. At the same time, the magnetic recording equipment 1 activates a reel drive motor (not shown) to rotate the take-up spool 6. When reaching the take-up reel 6, the leader block 80 is automatically captured in a retaining groove 6b formed in a reel hub 6a of the take-up reel 6. Thereafter, the magnetic tape 9 is wound around the reel hub 6a of the take-up reel 6 by the reel drive motor. The read-write head 7 records signals on the magnetic tape 9 or reads signals recorded on the magnetic tape 9 when the read-write head 7 is passed through by the magnetic tape 9.
Meanwhile, when winding a magnetic tape 9 supplied from a stock magnetic tape (which is called a pancake) on the tape reel 40 in the cartridge case 10, it is always intended to center a magnetic tape roll on the reel hub 421 of the tape reel 40 so as to left spaces or clearances between the magnetic tape roll and the upper and lower flanges 41 and 42, respectively. The problem that arises in winding the magnetic tape 9 on the tape reel 40 is what is called “irregular winding.” The term “irregular winding” as used herein shall mean and refer to a partial lateral protrusion of tape edge of the magnetic tape 9 from a side surface of a magnetic tape roll. The irregular winding occurs resulting from that the magnetic tape partly runs off the side surface of a magnetic tape roll at an edge due to a change in tension of the magnetic tape 9 following a decline in winding speed more specifically shown in FIGS. 6A to 6C.
Generally, tape winding is performed in such a winding pattern as initially caries out acceleration of a winding rate to a predetermined maximum rate at the beginning of winding, continues steady winding at the maximum rate and finally declines the winding rate as coming to the end of winding. The magnetic tape waggles or protrudes sideways due to changes in tension which occur correspondingly to the winding pattern. Such a change in tension is one of causes of irregular winding. In particular, since a change in tension becomes larger as the end of winding approaches, i.e. as a diameter of the magnetic tape roll becomes larger, the irregular winding takes place under the greater influence of a change in tension as the end of winding approaches as denoted by a reference sign 9a in FIG. 6A. It has been made appear that the irregularly-wound portion 9a of the magnetic tape roll could cause problems upon dropping of the magnetic tape cartridge 100 from above. For example, as shown in FIG. 7, if the magnetic tape cartridge 100 falls down against a horizontal surface such as a floor or a ground with the tape reel 40 kept in a horizontal position, the tape reel 40 receives strong impact T on the flanges 41 and 42 through the irregularly-wound portion 9a of the magnetic tape roll. As a result, the flanges 41 and 42 are instantaneously but greatly deflected in an axial direction of the reel hub 421. At the moment of this deflection, the upper flange 41 hardly hits against the irregularly wound portion 9a of the magnetic tape roll and folds down or damages a tape edge of the irregularly-wound portion 9a of the magnetic tape roll as shown in FIG. 6B. The tape edge folded down once is incapable of restoring its original state and remains folded or broken eve though the upper flange 41 is relieved of the impact T as shown in FIG. 6C.
The magnetic tape with its edge partially damaged wobbles sideways in the direction of tape width at the damaged portions due to sliding on the circumferential surfaces of the guide rollers 8 during movement in the tape path defined by the guide rollers 8 and, as a result of the edge damage, the read-write head 7 deviates off a recording track of the magnetic tape 9. Such tracking errors encountered by the magnetic tape 9 occur for the following reasons (1) and (2).    (1) When a lateral protruding edge of a magnetic tape caused due to irregular winding folds down, it is not improbable that a tape drive unit fails to detect a magnetic signal recorded on the magnetic tape in close vicinity to a tape edge which indicates a tape position.    (2) The fault of positional signal detection brings the magnetic tape to a halt or brings about a reduction in recording capacity.
For these reasons, it is conventional to restrain a sideways wobble of a magnetic tape by use of guide rollers while winding the magnetic tape onto a tape reel in order to prevent an occurrence of irregular windings. In other words, it has been thought that it is essential to contrive formation of a magnetic tape roll in a regular even form which has even side surfaces without protrusions of tape edge. For example, as described in Japanese Unexamined Patent Publication No. 2005-116093, a magnetic tape deed device is provided with a tape displacement detection means for detecting a displacement in a lateral direction of width of a magnetic tape and providing an output signal representative of the lateral displacement for a tape position correction means. The tape position correction means thrusts back the magnetic tape in an opposite lateral direction of width according to the output signal so as thereby to bring back the magnetic tape into a given path. The magnetic tape deed device is quite successful in forming a magnetic tape roll in a regular even form but has problems with the need for a tape displacement detection sensor and a displacement feedback circuit which derives up costs of the magnetic tape deed device and the need for such sophisticated winding control as is continued from beginning to end of winding of a tape onto a tape reel.